1. Field of the Invention
The present invention relates generally to a dynamic image displaying technology, and more particularly, to a motion picture detecting technology.
2. Description of Related Art
For image displaying, the content of each image frame changes if there is a motion object in the image. However, in some cases, the image being displayed is a static picture. Since static pictures and dynamic images are displayed in different manners, a degree of motion of the pictures is usually detected to provide a motion value which is used as reference for subsequent procedure in the displaying system. The motion value is within a predetermined range and corresponds to the degree of the motion. In general, a greater motion value indicates a greater change in the image content.
In a traditional way of detecting the motion pictures, the motion value is obtained by performing subtraction between data of two adjacent image frames. FIG. 1 illustrates a conventional circuit for detecting motion pictures. Referring to FIG. 1, the conventional motion picture detecting circuit includes an image frame buffer 100 and a motion detecting unit 102. Data of the image frame Fn is continuously inputted to the image frame buffer 100. The image frame buffer 100 may buffer data of two continuous image frames Fn and Fn−1. In addition, a current image frame Fn is also inputted to the motion detecting unit 102. The motion detecting unit 102 performs a subtraction between the data of the two image frames Fn and Fn−1 to obtain a motion value which is outputted through a path 104.
The motion value obtained through the path 104 according to the mechanism of FIG. 1 is related to the degree of change in the image frame data, which shows the image displaying is dynamic. FIG. 2 illustrates an implementation result of the circuit of FIG. 1. Referring to FIG. 2, three continuous image frames Fn-Fn+2 are taken as an example, where image data in the same locations 120′, 122′ 124′ of the image frames Fn-Fn+2 are compared. The image data of the locations 120′, 122′ 124′ may be compared on a pixel-by-pixel basis. Alternatively, the comparison may be conducted by comparing average image data of respective locations 120′, 122′, 124′. Greater image motion leads to greater change in the images of the same locations 120′, 122′, and 124′.
However, the method of FIG. 1 may easily cause mis-calculation. For example, an incorrect motion value may be obtained when only a local image is in motion, in which case subsequent image displaying may be processed in an improper way according to the incorrect motion.